grid bug

Grid bugs are the annoying gnats from Nethack. They are creatures of lightning, who shock you over and over with tiny bites. They are the simplest of all monster. Grid bugs tend to be on the first few levels, and have never been seen to leave a corpse. The grid bug death is considered a shameful defeat.

The grid bug has no magic resistance, a speed of 12 (about average) and a AC of 9. They are usually able to be killed in one connecting attack, or one magic spell. They are almost never a formidable foe.

The grid bug is a Nethack monster taken from the Tron mythos (and the only one at that). While not mentioned in the movie there is a bit of mentioning it from the novel form:

Tron looked to his mate and pilot. "I'm going to check on the beam connection, Yori. You two can keep a watch out for grid bugs." Tron paced forward along the slender catwalk that still seemed awfully insubstantial to Flynn, though he knew it to be amazingly sturdy. He gazed after Tron, asking himself what in the world a grid bug was, and hoping that the beam connection -- to which he'd given no thought whatsoever until this moment -- was healthy and sound."

The source has a bit more to say about the grid bug, though it is more along the lines of what they can and cannot do - most notably, a grid bug can only move in cardinal directions (North, East, South, West) and cannot move along the diagonals. Neither can a grid bug attack at an angle. This makes it paticularly easy to avoid a grid bug making death (even for an armorless and weaponless tourist) rather embarrassing. In dealing with shopkeepers, there is a test that makes certain that the shopkeeper does not become angry for a grid bug zapping it.

You turn into a grid bug!--More--
You become much too small for your shirt!--More--
You find you must drop your weapon!--More--
You can't even move a handspan with this load!

Being polymorphed into a grid bug gives you shock resistance and poison resistance, though its not that useful as one can see above. Furthermore, like the moster, when polymorphed into a grid bug one may not move along the diagonals. The player polymorphed into a grid bug has about the following stats:

Dlvl:1 $:842 HP:4(4) Pw:2(2) AC:9 HD:0 Overloaded

While a gridbug, you are constrained by the save movement rules as the
monster is - not able to move in diagonals.